Space heater

ABSTRACT

A space heater comprising a fuel reservoir, a primary combustion chamber having an exhaust gas outlet, an exhaust gas re-circulation duct, and a chimney. The exhaust gas re-circulation duct captures at least a portion of the exhaust gas exiting from the primary combustion chamber through the exhaust gas outlet and delivers the captured exhaust gas back to the primary combustion chamber. The chimney receives exhaust gas that is not captured by the exhaust gas re-circulation duct and expels the non-captured exhaust gas into the atmosphere surrounding the space heater.

FIELD OF THE INVENTION

[0001] This invention relates to space heaters, and in particular hydrocarbon burning space heaters that provide for the efficient combustion of hydrocarbons resulting in a low polluting exhaust stream.

BACKGROUND OF THE INVENTION

[0002] Space heaters have been designed in a wide variety of different configurations that utilize a host of different sources of energy to produce heat. In general, most space heaters can be broken down into one of two main categories; namely, electric heaters and those that generate heat through the combustion of hydrocarbon fuels. Electric heaters function through passing a current of electricity through a resistive element in order to generate heat. Hydrocarbon burning space heaters function through the combustion of a variety of different hydrocarbon fuels creating heat, along with various combustion bi-products.

[0003] Due to their generally lower operational costs, hydrocarbon burning space heaters are in many cases more attractive than electric heaters from an operational cost perspective. Unfortunately one of the more significant draw backs tending to minimize the use of hydrocarbon burning space heaters is their production of noxious and polluting emissions. Since the varieties of fuels that can be burned in a space heater are quite broad (for example, wood, cellulose, biomass, oil, kerosene, etc.) the combustion bi-products that can be created are also very diverse. In most instances such bi-products include carbon dioxide, carbon monoxide, and various nitrogen oxides and nitrogen compounds. In some cases combustion bi-products may also include a host of other more harmful components, depending upon the particular fuel being utilized.

[0004] On account of the polluting and noxious nature of exhaust gases produced through combusting such materials, standard space heaters that burn hydrocarbon fuels are typically vented to the atmosphere, thereby severely limiting their portability and usefulness within confined buildings or enclosures. This is particularly the case when heating oil or waste lubricating oil is used as the source of hydrocarbon fuel. Such oils typically contain higher amounts of complex based compounds that are not completely broken down through standard combustion means and often produce high amounts of polluting exhaust gases.

SUMMARY OF THE INVENTION

[0005] The invention therefore provides a space heater that is portable in nature and permits the burning of fuel oil or waste lubricating oil, as well as a variety of other fuels, in a highly efficient manner to eliminate or minimize the need for venting the exhaust outside of a building or enclosure.

[0006] Accordingly, in one of its aspects the invention provides a space heater comprising a fuel reservoir; a primary combustion chamber having an exhaust gas outlet; an exhaust gas re-circulation duct, said exhaust gas re-circulation duct capturing at least a portion of the exhaust gas exiting from said primary combustion chamber through said exhaust gas outlet and delivering said captured exhaust gas back to said primary combustion chamber; and, a chimney, said chimney receiving exhaust gas that is not captured by said exhaust gas re-circulation duct and expelling said non-captured exhaust gas into the atmosphere surrounding said space heater.

[0007] Further aspects and advantages of the invention will become apparent from the following description taken together with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0008] For a better understanding of the present invention, and to show more clearly how it may be carried into effect, reference will now be made, by way of example, to the accompanying drawings which show the preferred embodiments of the present invention in which:

[0009]FIG. 1 is a side elevational view of the space heater according to the present invention;

[0010]FIG. 2 is a vertical sectional view of the space heater shown in FIG. 1;

[0011]FIG. 3 is an exploded detail view of the fuel filler pipe and air intake assembly of the space heater shown in FIG. 1;

[0012]FIG. 4 is an enlarged detail view of area 4 of the space heater as shown on FIG. 1; and,

[0013]FIG. 5 is a sectional view taken along line 5-5 of FIG. 4.

DESCRIPTION OF THE PREFERRED EMBODIMENT

[0014] The present invention may be embodied in a number of different forms. However, the specification and drawings that follow describe and disclose only some of the specific forms of the invention and are not intended to limit the scope of the invention as defined in the claims that follow herein.

[0015] The space heater according to the present invention is shown in the attached drawings and noted generally by reference numeral 1. Space heater 1 is principally comprised of a fuel reservoir 2, a primary combustion chamber 3, an exhaust gas re-circulation duct 4, and a chimney 5. Through a thorough understanding of the invention it will be appreciated that space heater 1 could be constructed to burn a wide variety of different hydrocarbon fuels ranging from wood or cellulose products, to fuel oil, to kerosene, to naptha gas, etc. Although not specifically shown in the attached drawings, it will further be appreciated that with relatively minor modifications, space heater 1 could be adapted to burn either natural gas or propane.

[0016] Appreciating that space heater 1 could be configured to burn any one or more of the above fuels, the particular embodiment as shown in the attached drawings and described below is primarily focused upon the burning of liquid hydrocarbon fuels, including fuel oil, kerosene, and used or recycled motor or lubricating oils. To that extent, fuel reservoir 2 is comprised generally of an enclosed tank having a fuel filler pipe 6 that allows for fuel to be delivered into the tank, and at the same time permits the entry of combustion air into combustion chamber 3. Typically fuel reservoir 2 would be formed from a relatively thick gauged steel, or similar metallic product to safely contain the fuel therein.

[0017] It should be understood that while fuel reservoir 2 could be constructed and formed as a separate and distinct element from primary combustion chamber 3, in the embodiment of the invention as shown in the attached drawings fuel reservoir 2 also functions as primary combustion chamber 3. That is, after a quantity of fuel has been received within fuel reservoir 2, the fuel can be ignited allowing it to combust within the reservoir such that the upper portion of the fuel reservoir effectively operates as primary combustion chamber 3. An exhaust gas outlet 23 allows the combustion bi-products to be expelled from the chamber. Fuel within reservoir 2 may be ignited in a variety of different ways, including the insertion of a match or igniter through fuel filler pipe 3, or through the incorporation of electric or mechanical sparking devices. Once the fuel within reservoir 2 has been ignited, the rate of combustion will be primarily controlled through the adjustment of an air intake assembly 7 incorporated within fuel filler pipe 6.

[0018] As shown in FIGS. 1 and 2, exhaust outlet 23 is positioned in the central portion of primary combustion chamber 3 to permit the efficient release of exhaust gases from the combustion chamber and into chimney 5 during operation. To help encourage the movement of exhaust gases from the combustion chamber to the exhaust outlet, in the preferred embodiment the upper surface 12 of the combustion chamber is slightly convex in nature with its apex generally coincident with the centre of the exhaust outlet. The curvature of the upper surface of the combustion chamber will thus have a tendency to direct exhaust gases toward the exhaust outlet.

[0019] In the preferred embodiment, space heater 1 further includes a secondary combustion chamber 8 that receives exhaust from primary combustion chamber 3 and subjects that exhaust to secondary combustion. Referring again to FIGS. 1 and 2, secondary combustion chamber 8 is generally formed through enlarging the diameter of a portion of the length of chimney 5. In this manner, secondary combustion chamber 8 will be positioned vertically above primary combustion chamber 3 (and exhaust outlet 23) and will receive all exhaust gases generated through the burning of fuel in the primary combustion chamber.

[0020] Spaced about a portion of the exterior surface of secondary combustion chamber 8 is a plurality of air intake aperatures 9 that permit the entry of additional combustion air into the secondary combustion chamber. While the particular configuration of the air intake aperatures may vary widely, in the preferred embodiment they are comprised of inwardly directed and upwardly opening slots within the exterior surface of secondary combustion chamber 8 (see FIGS. 4 and 5). Through the configuring of air intake apertures 9 in this manner, exhaust gases flowing upwardly through secondary combustion chamber 8 will have a tendency to draw additional combustion air into the secondary combustion chamber through aperatures 9, allowing the oxygen rich combustion air to readily mix with the hot exhaust gases. Volatile or unburned compounds and gases present in the exhaust stream will react with oxygen in the combustion air (introduced into secondary combustion chamber 8 through aperatures 9) resulting in further combustion or oxidation of such compounds and gases. This “secondary burning” of the exhaust gases results in increased heat production and reduced overall emissions from the space heater, including emissions of carbon monoxide, other carbon based compounds and gases, and nitrogen oxides. There is also a tendency to reduce emissions of volatile hydrocarbon fuel compounds that may escape primary combustion chamber 3.

[0021] As indicated above, in the preferred embodiment of the present invention space heater 1 includes an exhaust gas re-circulation duct 4 that captures at least a portion of the exhaust gas exiting from primary combustion chamber 3 and delivers or re-circulates the captured exhaust gas back into the primary combustion chamber. Typically exhaust gas re-circulation duct 4 would be comprised of an enclosed duct having a circular or rectangular cross section with an upper end 10 terminating within secondary combustion chamber 8 and a lower end 11 terminating within primary combustion chamber 3. Upper end 10 preferably includes a funnel shaped hood 14 that aids in capturing exhaust gases passing upwardly through secondary combustion chamber 8.

[0022] It will be appreciated that hood 14 will be heated to a relatively high temperature during operation of space heater 1. Since it is generally Centre within the exhaust stream of secondary combustion chamber 8, hood 14 may be heated to temperatures approaching, or in excess of, 1000 degrees Celsius. At temperatures in this range the hood will also serve as a means to assist in the incineration of volatile compounds and unburned fuel or other hydrocarbons present in the exhaust stream.

[0023] The configuration of re-circulation duct 4 shown in FIGS. 1 and 2 is but one configuration that could be utilized. In this configuration lower end 11 of the duct intersects upper convex surface 12 of combustion chamber 3 at a point distant from its center. In this fashion there will be tendency for exhaust gases produced from the combustion of fuel within combustion chamber 3 to pass upwardly through exhaust gas outlet 23 and out of combustion chamber 3 into secondary combustion chamber 8 without travelling through re-circulation duct 4.

[0024] In an alternate embodiment of the invention, re-circulation duct 4 could extend downwardly through upper convex surface 12 of combustion chamber 3 and into the combustion chamber to reduce the possibility of exhaust gases travelling upwardly through the re-circulation duct. However, in this embodiment the lower end of the re-circulation duct must be positioned such that it all times remains above the upper most level of any liquid fuel (shown as 24 in FIG. 2) stored within fuel reservoir 2. In yet a further embodiment, lower end 11 of re-circulation duct 4 could intersect the side surface 13 of primary combustion chamber 3, in which case once again the point of intersection should be maintained above the upper fuel level.

[0025] It will thus be appreciated from an understanding of the above described structure that as heated exhaust gases pass from primary combustion chamber 3 upwardly and through secondary combustion chamber 8 they will eventually reach the general vicinity of hood 14. At the same time, the combustion of fuel in primary combustion 3 will decrease the vapour pressure causing a vacuum situation to be established within primary combustion chamber 3 thereby “drawing” fresh combustion air into combustion chamber 3 through air intake assembly 7. Air and gases will also be drawn downwardly into combustion chamber 3 through re-circulation duct 4. Upon the initial start-up of space heater 1, the lower temperature of gases within re-circulation duct 4 will assist in establishing a downward flow through the re-circulation duct and into combustion chamber 3.

[0026] To assist in controlling the rate of combustion and the circulation of gases through re-circulation duct 4, air intake assembly 7 includes a control member or plate 15 that can be moved to reduce or enlarge the size of an air intake slot 16 in the assembly. By effectively reducing the size of slot 16 the amount of air drawn through air intake assembly 7 will be reduced, having the effect of reducing the rate at which fuel is consumed within combustion chamber 3. Similarly, adjusting control plate 15 to effectively increase the size of air intake slot 16 will have the net effect of increasing the amount of oxygen present within combustion chamber 3 and increasing the rate of consumption and burning of the hydrocarbon fuel. Accordingly, through the adjustment of air intake assembly 7, the rate of fuel consumption (and hence heat generation), as well as the rate of re-circulation through duct 4, can be controlled.

[0027] Space heater 1 is also preferably equipped with a damper 17 positioned between primary combustion chamber 3 and secondary combustion chamber 8. Damper 17 has an open position where it permits generally unabated movement of exhaust gases from primary combustion chamber 3 to secondary combustion 8, and a closed position where it impedes the movement of exhaust gases between the two combustion chambers. To shut the combustion process down completely, control plate 15 is first rotated so as to effectively block air intake slot 16 and prevent further combustion air from entering combustion chamber 3. Thereafter damper 17 is moved to its closed position to effectively extinguish the flame in combustion chamber 3.

[0028] In order to increase the efficiency of space heater 1, and in particular the efficiency of the secondary burning or combustion occurring within secondary combustion chamber 8, in one embodiment of the present invention secondary combustion chamber 8 includes a pre-heater 18. The primary function of the pre-heater is to elevate the temperature of the secondary combustion chamber and accelerate the rate of secondary combustion, particularly upon start-up. Pre-heater 18 may take a variety of different forms, including electrical heating elements wrapped about a portion of secondary combustion chamber 8. In the embodiment shown in FIG. 2, pre-heater 18 comprises a secondary fuel reservoir 19 capable of receiving a quantity of combustible fuel. A filler pipe 20 would typically extend through the outer sidewall of the secondary combustion chamber to allow for the placement of fuel within secondary fuel reservoir 19.

[0029] To operate pre-heater 18 fuel, contained within secondary fuel reservoir 19 is ignited through the use of a match or other ignition source, including an electronic or mechanical sparking device. Once ignited, the burning fuel will cause secondary combustion chamber 8 to be heated above room temperature. After the secondary combustion chamber has been sufficiently pre-heated, the fuel within primary combustion chamber 3 may then be ignited causing exhaust gases to move upwardly into secondary combustion chamber 8 where, through prior pre-heating, additional burning, oxidation or combustion of unburned fuel and combustion bi-products in the exhaust gas can take place. To minimize the production of smoke and pollutants upon the start-up of space heater 1, and when burning fuel in pre-heater 18, preferably the fuel utilized within secondary fuel reservoir 19 is of a highly volatile nature, such as kerosene, naptha gas, methyl hydrate or similar fuels.

[0030] Through the incorporation of secondary combustion chamber 8, re-circulation duct 4, and pre-heater 18 it will be appreciated and understood that space heater 1 will provide a highly efficient means to combust hydrocarbon fuels with a minimal production of noxious or polluting bi-products. The pre-heating of secondary combustion chamber 8 helps to ensure that the secondary combustion chamber is at a sufficiently elevated temperature to allow for secondary combustion or oxidation of exhaust gases when they begin to pass from primary combustion chamber 3 into secondary combustion chamber 8. Air intake aperatures 9 help to provide sufficient oxygen to the secondary combustion chamber for the further reaction and burning of particulate and other volatile elements that may be entrained within the exhaust stream. The utilization of recirculation duct 4 causes a portion of the exhaust gas travelling upwardly through secondary combustion chamber 8 to be captured and returned back to primary combustion chamber 3 where any remaining fuel or other combustible materials can be further burned or oxidized before being expelled to the atmosphere.

[0031] To provide yet a further means to reduce pollutants expelled from space heater 1, in one embodiment of the invention re-circulation duct 4 and/or chimney 5 may be equipped with an afterburner 21. In the preferred embodiment, afterburner 21 is preferably comprised of either a catalytic converter or a plurality of high energy electrodes. Where the afterburner is comprised of a catalytic converter, the particular catalyst can be chosen from a host of different commercially available catalysts specifically designed for burning emissions from particular types of fuel sources. Such commercially available catalysts are usually highly efficient in reducing polluting carbon and nitrogen compounds in exhaust streams.

[0032] Where the fuel being burned contains more complex compounds that are difficult to break down at normal combustion temperatures, high energy electrodes 22 may be utilized in the place of, or in addition to, a more standard commercially available catalytic converter. The electrodes are arranged such that they create a high energy plasma arc within the exhaust gas stream in order to help break down complex compounds at highly elevated temperatures. For example, where the fuel utilized in space heater 1 is recycled lubricating oil, it may include toxic elements such as PCB's that are not normally broken down or rendered harmless at normal combustion temperatures. Passing the PCB's through high energy plasma arcs created between electrodes 22 will expose them to temperatures upwards of 3000° and have the effect of breaking the PCB compounds down into less complex elements that are less toxic nature, and that may be more readily burned or consumed through combustion in chambers 3 or 8, or in an associated catalytic converter.

[0033] It is to be understood that what has been described are the preferred embodiments of the invention and that it may be possible to make variations to these embodiments while staying within the broad scope of the invention. Some of these variations have been discussed while others will be readily apparent to those skilled in the art. 

I claim:
 1. A space heater comprising: (i) a fuel reservoir; (ii) a primary combustion chamber having an exhaust gas outlet; (iii) an exhaust gas re-circulation duct, said exhaust gas re-circulation duct capturing at least a portion of the exhaust gas exiting from said primary combustion chamber through said exhaust gas outlet and delivering said captured exhaust gas back to said primary combustion chamber; and, (iv) a chimney, said chimney receiving exhaust gas that is not captured by said exhaust gas re-circulation duct and expelling said non-captured exhaust gas into the atmosphere surrounding said space heater.
 2. The device as claimed in claim 1 including a secondary combustion chamber, said secondary combustion chamber receiving said exhaust gas from said primary combustion chamber and subjecting said exhaust gas to secondary combustion.
 3. The device as claimed in claim 1 wherein said primary combustion chamber includes an air intake assembly to allow for entry of combustion air into said combustion chamber.
 4. The device as claimed in claim 2 wherein said secondary combustion chamber is positioned generally vertically above said primary combustion chamber, said secondary combustion chamber including a plurality of air intake aperatures to allow for the entry of combustion air into said secondary combustion chamber.
 5. The device as claimed in claim 2 including a damper positioned between said primary and said secondary combustion chambers, said damper having an open and a closed position, when in said open position said damper permitting generally unabated movement of exhaust gas from said primary combustion chamber to said secondary combustion chamber, when in said closed position said damper impeding the movement of exhaust gas from said primary combustion chamber to said secondary combustion chamber.
 6. The device as claimed in claim 2 wherein said secondary combustion chamber includes a pre-heater to elevate the temperature of said secondary combustion chamber.
 7. The device as claimed in claim 6 wherein said pre-heater comprises a secondary fuel reservoir positioned about said secondary combustion chamber, said secondary fuel reservoir receiving a quantity of fuel for combusting therein.
 8. The device as claimed in claim 6 wherein said pre-heater comprises an electric heating element.
 9. The device as claimed in claim 1 wherein said exhaust gas re-circulation duct includes an afterburner, said afterburner assisting in the combustion of hydrocarbons and other compounds in said captured exhaust gas.
 10. The device as claimed in claim 9 wherein said afterburner comprises a catalytic converter.
 11. The device as claimed in claim 9 wherein said afterburner includes one or more high energy electrodes, said electrodes creating a high energy plasma arc within said exhaust gas re-circulation duct.
 12. The device as claimed in claim 1 wherein said chimney includes an afterburner, said afterburner assisting in the combustion of hydrocarbons and other compounds in said exhaust gas passing through said chimney.
 13. The devices claimed in claim 12 wherein said afterburner comprises a catalytic converter.
 14. The device as claimed in claim 12 wherein said afterburner includes one or more high energy electrodes, said electrodes creating a high energy plasma arc in said chimney.
 15. The device as claimed in claim 1 wherein said exhaust gas re-circulation duct and said chimney each include afterburners, said afterburners assisting in the combustion of hydrocarbons and other compounds passing therethrough. 